More particularly, the invention relates to a process for preparing substantially caffeine-free extracts containing polyphenols derived from epigallocatechin in their natural ratio.
Caffeine is known to have undesirable effects on the cardiovascular system as well as a mutagenic effect, and it is usually removed from such polyphenol fractions by extraction with carbon dioxide under hypercritical conditions or with chlorinated solvents. However, the above techniques are not intended to, nor are they capable of, producing extracts with reproducible amounts of the polyphenol compounds responsible for beneficial biological effects.
The polyphenols, characteristic of the tea plant, have recently been the object of a great interest due to their strong antioxidant effect, as described in, for example, Zhao B. et al, Cell Biophys. 14, 175 (1989) and Huang M. T. et al., Carcinogenesis 13, 947 (1992). Such an effect is apparently related to some extent to the capability of some of these polyphenols (for example epigallocatechin-3-O-gallate) of inhibiting formation of neoplasias artificially induced in the laboratory animals (Conney A. H. et al., Prev. Med. 21, 361 (1992) and Mukhtar H. et al., J. Invest. Dermatol. 102, 3 (1994)).
Moreover, some recent epidemiological studies evidenced how the consumption of large amounts of green tea is associated with a lower incidence of degenerative chronic diseases, for example some forms of cancer and atherosclerosis, see, e.g., Kono, S. et al., Jpn. J. Cancer Res. 79, 1067 (1988); Oguni I. et al., Agric. Biol. Chem. 52, 1879 (1988); Kato I et al., Jpn J. Cancer Res. 81, 1101 (1990) and Kono S. et al., Prev. Med. 21, 526 (1992).
At present, the mechanisms of action of the substances contained in green tea derivatives have not yet been completely elucidated, apart from the general antioxidant effect described above. It has, however, been determined that the polyphenol component of green tea is capable of exerting a differentiated cytotoxic effect depending on the type of cell which is studied and that such a differentiation is particularly related to the selective targeting which some of these polyphenol molecules have towards sub-cell sites such as mitochondria.
Therefore, there has been a long-felt need, which is now met by the present invention, for a method of extracting Camellia sinensis that produces extracts containing a predetermined, i.e., "standardized" amount of polyphenols and wherein the caffeine content of these extracts is minimized, if not eliminated totally.